Benefits of Soda Blasting
• Soda is granular, suitable for use in pressure pots or in cabinet systems.
• Soda crystals are sharp and provide outstanding cleaning/stripping performance when delivered under relatively low pressure but with high velocity.
• Soda is “friable,” meaning that it fractures into smaller particles. This increases cleaning performance while softening blasting impact. Unlike other blast media, soda is relatively soft and doesn’t damage metal surfaces.
• Soda is nontoxic and nonhazardous, with a nearly benign pH of 8.2.
• Soda is water soluble and easy to rinse clean.
• Soda leaves no abrasive “grit” that can damage moving parts.
A wide range of blasting media is available, each with its own characteristics. Depending on the material to be blasted, including cast-iron, cast-aluminum, steel, etc., and type of component including blocks, heads, manifolds, pistons, connecting rods, etc., and the desired surface finish, attention must be paid to selecting the appropriate type of media for the specific application.
Sand
Commonly available silica sand is far too aggressive and should never be used on any engine-related surfaces. This is often used on car components, body panels, frame rails, and suspension parts. But sand is so abrasive that it literally eats away at soft aluminum, pits cast-iron, and does irreparable harm to other steel parts.
Glass Bead
Depending on the specific grade (grit), glass bead media is produced as preformed tiny balls, which, depending on the grade of glass, produce a smoother and “brighter” finish than angular abrasives (results in a matte satin finish). Glass bead, like most blasting media (other than soda), does not act as a desiccant, so the component must be dry and grease-free prior to blasting. Grease, oil, etc., are eventually removed during blasting, but over the long haul, you end up contaminating the glass bead in the hopper. The same applies to layers of paint that flake off easily. Large flakes (larger than, say, your little fingernail) collect in the hopper and eventually clog the feed tube. When/if this occurs, a quick fix is to place the tip of a bolt into the gun nozzle and hit the foot pedal. This causes the bead to “back-flush,” temporarily clearing the system for continued use. Regardless, glass bead or any blast media should be routinely changed to remove foreign contaminants and to renew the capabilities of the media.
What most people don’t realize is that a huge range of glass bead is available, from very, very aggressive down to ultra-fine grades. All glass bead is not created equal, so pay attention to what you’re buying. A fine-grade glass bead produces a matte satin finish.
Crushed Glass Grit
Similar to glass bead in initial appearance, but the particles feature random shapes and sharper edges. This cuts faster and is more aggressive than glass bead, and produces a medium texture.
Soda
Unlike hard and aggressive media such as sand, baking soda (sodium bicarbonate) is able to strip to bare metal without abrading the parent surface. Soda media is “softer” than other types of media and is “friable,” which means that the soda crystals break down upon impact (akin to throwing a snowball against a brick wall as opposed to throwing a rock against the same wall). Essentially, soda does the job without damaging the metal. Because soda is “softer,” and because it is water soluble, it leaves no abrasive grit that can damage moving parts (such as hood or door hinges).
Soda is nontoxic and nonhazardous, making its use far safer than other abrasive or chemical stripping methods. However, dry blasting generates a great deal of dust. For this reason, it is recommended that a dust mask be used, as well as eye and hearing protection.
In addition to blasting sheet metal material for body refinishing/restoration, soda is also an outstanding choice for blast-cleaning components such as frames, suspension parts, brake parts, engine components, etc. Because no hard abrasive grit is present, components such as engine blocks, cylinder heads, intake manifolds, etc., can be cleaned and then rinsed without concern for trapping damaging grit particles.
Aluminum Oxide
Depending on blast pressure, this can be very aggressive and leaves a coarse, textured finish. It’s economical, but be aware that it cuts very quickly and removes more metal. Used properly (level of blast pressure), you can avoid a too-rough finish.
Speed-Beed
This is a hybrid mix of 50- to 80-grit glass bead and 80-grit aluminum oxide. This provides faster cutting than glass bead but is not as aggressive as aluminum oxide.
Plastic Bead
Generally available in 30- to 40-grit size, plastic bead is good for removal of paint and surface rust. Plastic bead produces less blasting heat. This may be a good choice for cleaning gears, tooling, etc., because it doesn’t alter dimensions, and it doesn’t etch the surface.
A Special Note Regarding Intake Manifolds
Obviously, intake manifolds (single plane or dual plane) feature intake runners. Even after careful degreasing, blasting with an abrasive media can be dangerous, especially when dealing with a dual-plane intake manifold where you don’t have easy reach and access to all port surfaces. Fine media particles can embed into the material (or can be stuck in a remote piece of sludge or carbon), increasing the chance of that media eventually being sucked into the engine. If you do decide to blast an intake manifold with, for example, glass bead, you need to make absolutely certain that you eliminate any possibility of trapped particles inside the runners. If you feel the need to blast and you’re worried about leaving harmful particulates behind, soda is the best choice because it’s water soluble when rinsed. Even though the soda doesn’t pose a threat to the engine, any rust scale, dirt, etc., that’s held captive poses a serious risk. Regardless of the type of media you use, you still need to flush the runners surgically. If you do media-blast an intake manifold where you are uncertain about hidden debris, a follow-up cleaning in an ultrasonic unit along with a hot, soapy rinse/flush should remove any remaining contaminants.
Walnut Shell
Crushed walnut shell (aside from being biodegradable) is relatively gentle and is ideal for preserving surface micro finish while cleaning. Under controlled conditions, it’s also useful for those instances where you want to remove paint topcoats but retain the primer layer. Like most media, walnut shell is available in a variety of grit, from extra coarse to extra fine.
Corncob
Corncob is even softer, good for finalizing a nice satin finish. Either walnut shell or corncob can be very effective in removing paint and rust, without eating away at the base metal. And these organic types of media are relatively cheap.
A fine grade of walnut shell or corncob doesn’t remove any of the metal, it doesn’t etch or scratch softer metals, and the material doesn’t imbed into the metal surface. Walnut or corncob are great choices where a finer finish and retention of detail is important.
Steel Grit
A fine grade of steel grit leaves a relatively smooth finish. Steel cuts very fast and lasts longer